EP0676535A1 - Catalytic converter for the catalytic treatment of exhaust gases - Google Patents

Abstract

The catalyst has a housing (203) in which catalyst material (210) is contained. Between areas of this material is located an inner hollow chamber (221) and between the catalyst material and at least a part of the housing is an outer hollow chamber (222). The catalyst material consists of plate components (213, 214) which limit through passages (217) from the inner hollow chamber to the outer hollow chamber. At least one plate component from each pair of adjacent plate components has raised formations. The catalyst material consists of at least two packets of plate components and the through passage limited by them run away from the inner hollow chamber on different sides. <IMAGE>

Description

The invention relates to a catalytic converter for the catalytic treatment of exhaust gas.

The catalytic converter is in particular provided to purify and / or detoxify exhaust gas generated by a gasoline internal combustion engine of a motor vehicle, for example an automobile, or possibly by another internal combustion engine, i.e. rid of pollutants by converting them through a chemical reaction.

Known catalysts for treating exhaust gas have a housing with an inlet and an outlet. The housing contains catalytic agent with a catalytic converter body, often referred to as a substrate, with passages for the exhaust gas or with a plurality of catalytic converter bodies through which flow passes during operation. The surfaces delimiting the passages are provided with a coating which has a catalytically active material with at least one noble metal.

Many of these known catalysts have the disadvantage that the exhaust gas flowing in through the inlet is distributed only over a small exhaust gas entry area of the (first) catalyst body and / or only unevenly over this exhaust gas entry area and / or that the exhaust gas is between the inlet and the (first) catalyst body and / or in the latter, even at the start of operation, releases a large amount of heat to the environment via the wall of the housing relatively quickly. If the exhaust gas only on a small exhaust gas inlet area and / or If this is distributed irregularly, this increases the pressure drop or back pressure and also causes a reduction in the efficiency and thus an increase in the required catalyst body volume, the required noble metal and the production costs. When the internal combustion engine and catalytic converter are cold started, the rapid and large amount of heat given off by the catalytic converter means that it takes a relatively long time until the or each catalytic converter body reaches the temperature required for efficient exhaust gas treatment.

Various catalysts are disclosed in EP-A 0 514 326, which already largely avoid the disadvantages described above. From this publication, for example, catalysts are known with a housing which has a jacket and contains catalyst means with an annular catalyst body. This consists of a package of ring-shaped sheet metal elements. The successive sheet metal elements have mutually crossing waves. The sheet metal elements are held together by holding means. These have bolts which penetrate holes in the sheet metal elements and are welded at their ends to a flat plate or housing wall. An opening of the housing is connected to an inner cavity enclosed by an inner lateral surface of the catalyst body. Another opening of the housing is connected to an outer cavity which is present between the casing of the housing and an outer casing surface of the catalyst body. The catalyst body has passages running from the inner to the outer cavity, which are evenly distributed along the circumference of the outer surface. The jackets of the housings and the jacket surfaces of the catalyst bodies of these known catalysts are circular or oval in cross-section and have cross-sectional dimensions that are substantially larger than the axial dimensions of the jackets or catalyst bodies.

The annular sheet metal elements of these known catalysts are usually punched out of square metal sheets or from metal strips during production. This creates a relatively large amount of sheet metal waste, which increases the cost of manufacturing the catalysts.

When catalysts are to be installed on the underside of an automobile, there is often little space available. The space available can be different for different types of automobiles. In order to enable short exhaust gas lines, it may be desirable in certain cases, for example, if the jacket has a relatively flat shape in cross-section and thus a cross-sectional dimension of the jacket is relatively small compared to the amount of exhaust gas to be treated. In other cases, it could be advantageous if the jacket were approximately triangular in cross section. Furthermore, it would be advantageous in certain cases if the (maximum) cross-sectional dimension of the jacket is smaller than its length.

In the known catalysts, the catalyst means or catalyst body of which have sheet metal elements and passages running from an inner to an outer cavity, the cross-sectional area of the passages increases from the inside to the outside. This can increase the need for catalytically active precious metal and thereby increase the manufacturing costs.

A catalyst known from FR-A 2 617 903 has a housing which contains catalyst means with a package of annular sheet-metal elements which have coatings with catalytically active material. The inlet of the catalyst opens into a cylindrical inner cavity enclosed by the catalyst means. There is an outer cavity between the inner surface of the housing and the catalyst means which is connected to the outlet of the catalyst. The sheet metal elements of the catalyst means are generally conical, but at least one sheet metal element from each A pair of mutually adjacent sheet metal elements is provided with waves or humps, so that the sheet metal elements limit passages running together in pairs from the inner cavity to the outer cavity. The sheet metal elements are arranged in a cage which has an annular flange at the inlet-side end of the package, a plate at the other end and some rods connected to the latter and the annular flange and distributed around the package.

The length of the inner cavity of this known catalyst is much larger than its diameter. The gas flowing through the inlet into the inner cavity during operation therefore forms a jet which is only deflected when it hits the plate. The current density of the exhaust gas flowing through the passages of the catalyst means is therefore substantially lower in the vicinity of the inlet than in the vicinity of the end of the catalyst means facing away from the inlet. Such an inhomogeneous flow through the catalyst means results in poor utilization of the catalytically active material, so that the catalyst becomes larger and more expensive than it would be with a homogeneous flow through the catalyst means. In addition, turbulence occurs in the inner cavity, which increases the pressure drop of the exhaust gas flowing through the catalytic converter. In addition, a lot of waste is generated in the production of the conical sheet metal elements from sheet metal sheets or sheet metal strips. Furthermore, it is difficult to form conical sheet metal elements with waves or humps. According to the last-cited publication, the sheet metal elements can possibly be connected to one another or to the ring flange or the plate by spot welding. Since the sheet metal elements only touch at least in part at linear wave apices or point-shaped hump peaks and also have coatings, it would be very difficult and expensive to weld all sheet metal elements together in pairs. In addition, the sheet metal elements can deform relatively strongly despite such point connections and move against each other. Since the sheet metal elements vibrate when using the catalyst, are exposed to other accelerations and temperature changes, there is a great risk that the sheet metal elements and especially their coatings will be damaged.

A catalyst known from FR-A 2 075 691 has an oval cross-section housing with an inlet and an outlet. A V-shaped catalyst body arranged in the housing has two hollow legs which are delimited on the inside by perforated inner walls and on the outside by perforated outer walls and contain a particulate material which serves for the catalytic treatment of the exhaust gas. The inlet opens into an internal cavity between the perforated inner walls of the catalyst body. An outer cavity present between the perforated outer walls of the catalyst body and inner surface sections of the housing is connected to the outlet.

The particles of the particulate material are not described in more detail in FR-A 2 075 691, but presumably consist of a ceramic core which is coated with catalytically active material. When a catalytic converter is connected to an internal combustion engine of an automobile, vibrations caused by the engine and accelerations caused by driving when the latter are used act on the catalytic converter. The particles of the particulate material are therefore moved, abutting against one another and against the walls of the catalyst body, and also sliding against one another and on the walls. The particulate material is therefore destroyed in a short time by abrasion and breakage when using the catalyst.

The diameter of the mouth opening of the inlet of FR-A 2 075 691 opening into the inner cavity known catalyst is much smaller than the length of the inner cavity and than the width of the section of the inner cavity adjoining the mouth opening of the inlet. When using the catalyst, therefore, a large part of the gas flowing at high speed from the inlet into the inner cavity forms a relatively thin jet, which only hits the perforated inner surface of the catalyst body at a large axial distance from the inlet. Large vortices arise in the areas of the inner cavity located to the side of the mouth of the inlet. The current density of the exhaust gas in the catalyst body is therefore very inhomogeneous. This results in poor utilization of the catalytically active material and a large pressure drop or back pressure. The vortices created in the inner cavity increase the pressure drop or back pressure even more.

The invention has for its object to provide a catalyst which eliminates disadvantages of the known catalysts and in particular the shapes and dimensions of the housing and the catalyst means can be adapted well to the available space, the catalyst even with relatively large, axial Dimensions of the catalyst means and of the inner cavity should enable a uniform distribution of the exhaust gas over all passages of the catalyst means, low pressure losses, good starting properties, a stable connection of the sheet metal elements and cost-effective production.

This object is achieved according to the invention by a catalyst for the catalytic treatment of exhaust gas, with a housing and catalyst means arranged therein, an inner cavity located at least in part between regions of the catalyst means and one between the catalyst means and at least one part of the housing, the outer cavity is present, the catalyst means having sheet metal elements that extend from the inner Limiting the void leading to the outer cavity, and wherein at least one sheet metal element of each pair of adjacent sheet metal elements has ridges and wherein the catalyst is characterized in that the catalyst means have at least two packets of sheet metal elements, that the sheet metal elements belonging to the same package cling to them , define mutually parallel planes of curvature and that the passageways delimited by the various packages run away from it on different sides of the inner cavity.

Advantageous further developments of the catalyst emerge from the dependent claims.

The ends of the passages opening into the inner or outer cavity are also referred to below as inner or outer ends of the passages.

According to the invention, the catalyst means have at least two packages of sheet metal elements. Each of these sheet element packages delimits a group of passes. The different packages and the different groups of passages can then be at least at the outer ends of the passages at a distance from one another which is substantially greater than the distance from adjacent sheet metal elements belonging to one and the same package and as the distance from adjacent ones in one and the same sheet element package existing passages.

According to the invention, a sheet metal element of each pair of immediately adjacent sheet metal elements is provided with elevations. The other sheet metal element of each pair of adjacent sheet metal elements can then be flat. Each package of sheet metal elements then consists of alternately successive, first and second sheet metal elements, the first sheet metal elements having elevations and the second sheet metal elements being essentially flat.

The elevations of a sheet metal element consist, for example, of straight, mutually parallel shafts or humps, which preferably protrude on both sides of a central plane and preferably have a rounded, for example circular, outline in a plan view of the sheet metal element.

However, it can also be seen that all sheet metal elements have elevations, for example waves. The waves of the successive sheet metal elements can then intersect, for example.

Each sheet metal element defines two osculating planes or flat osculating surfaces, each of which nestles against one of the two surfaces of the sheet metal element. If a sheet metal element has elevations, the osculating planes nestle at the highest points of the elevations, that is, for example, at the apex lines of the waves or at the summit points of the humps. If a sheet metal element is flat, the nesting planes defined by it are identical to the two flat surfaces of the sheet metal element.

The successive sheet metal elements of a package of sheet metal elements can then lie against one another in pairs at the nesting planes. The nestling levels then form - with the exception of the nesting levels located at the two ends of a package - contact levels in which the mutually adjacent sheet metal elements touch in places.

The formation of the catalyst means from at least two packages of sheet metal elements makes it possible to adapt the shapes and dimensions of the catalyst means and of the housing and in particular the cross-sectional shape and the cross-sectional dimensions of the jacket to the space available for the catalyst. For example, two and only two packages of sheet metal elements can be provided. The two sheet metal element packages can be on opposite sides of a central plane running between them through the inner cavity and contain passages running away from it and away from the inner cavity. The housing can then have a relatively flat cross-sectional shape compared to a housing with a circular cross section. The housing can then furthermore have a first cross-sectional dimension measured at right angles to the said central plane and a second cross-sectional dimension measured parallel to the central plane, which is smaller than the first cross-sectional dimension. The second, smaller cross-sectional dimension can be, for example, at most 70% or at most 60% or even only at most 50% of the first, larger cross-sectional dimension, depending on the available space. This makes it possible, for example, to install the catalytic converter in the line of an exhaust system of an automobile at a point where there is little space available in a direction transverse to the line and to the casing of the catalytic converter, for example in the vertical direction.

However, it is also possible to provide catalyst means with three packs of sheet metal elements and to form the casing of the housing in such a way that it defines a triangle in cross section, but the casing can have rounded transitions instead of corners. In certain cases, an approximately triangular-shaped jacket can facilitate installation. Such a catalyst can then be arranged, for example, under the floor of an automobile in such a way that the underside of the jacket is formed by a horizontal triangular side.

Catalyst means can also be provided which have four or more packs of sheet metal elements distributed around the internal cavity. In cross section, the casing of the housing can then define a polygon with corners replaced by rounded transitions and / or be more or less circular.

The maximum cross-sectional dimension of the catalyst means resulting in cross-sections perpendicular to the axis of the jacket can, for example, be smaller than the maximum axial dimension of the catalyst means. Likewise, the maximum cross-sectional dimension of the shell and the entire housing can be smaller than the axial dimension of the shell and the entire housing.

Each sheet metal element has a top view - i.e. in a projection at right angles to the nesting planes defined by the sheet metal element - preferably a square-shaped outline. Furthermore, each sheet metal element preferably has at least two straight, mutually parallel edges in plan view or in the above-mentioned projection, for example at least the two edges adjacent to the inner cavity or the outer cavity in the above-mentioned projection being straight and parallel to one another. Furthermore, the two other edges of each sheet metal element in the above-mentioned projection are preferably straight and parallel to one another, so that the sheet metal element forms an oblique-angled or right-angled parallelogram in plan view or in the above-mentioned projection. This makes it possible to produce the sheet metal elements with at most minimal sheet metal waste from strips with parallel longitudinal edges or from square, square or rectangular sheets.

The catalyst preferably has an inlet for the exhaust gas connected to the inner cavity. The interior space or passage delimited by the inlet preferably opens directly into the inner cavity which is at least partially limited by the catalyst means in cross section. In addition, the interior or passage of the inlet preferably has essentially, ie at least approximately or for example exactly the same cross-sectional shape and essentially, ie at least approximately or exactly the same cross-sectional dimensions as its mouth opening into the inner cavity the inner cavity. Furthermore, the inner cavity preferably has at least one free region adjoining the catalyst means, the cross-sectional area of which decreases away from the inlet. The cross-sectional area of the or each free region of the inner cavity preferably takes at least approximately or exactly linearly with the distance from the inlet at least in the largest part of the extension extending from the inlet and for example along the entire extension of the inner cavity and the catalyst means extending away from the inlet from. The cross-sectional area of the inner cavity may range from the point at which the closest passages of catalyst means open into the inner cavity to the point where the most distant passages open into the inner cavity, for example decrease by at least 50% or even at least by 80% and practically to zero. This design of the inlet and the inner cavity enables the exhaust gas flowing into the inner cavity to operate evenly with an axial dimension of the latter that is large compared to the cross-sectional dimensions of the interior or passage of the inlet and of the inner cavity, for all passages of the catalyst means distribute, which contributes to a good utilization of the catalytically active material and thus to low manufacturing costs compared to the amount of exhaust gas to be treated per unit time. In addition, the described design of the inlet in combination with the decrease in cross section of the or each free area of the inner cavity counteracts the formation of turbulence, which in turn makes it possible to keep the pressure loss low.

As already described, the catalyst is preferably designed such that the inlet opens directly into the inner cavity, which is at least partially delimited by the catalyst means. The exhaust gas can then between the outflow from the inlet and the inflow into the passages of the catalyst means at most with small Areas of the wall of the housing come into contact. The cross section of the internal cavity may even be substantially limited along its entire circumference and essentially exclusively by the catalyst means, so that the exhaust gas between the outflow from the inlet and the inflow into the passages of the catalyst means is practically not in contact with the wall of the catalyst Housing can get. Furthermore, the inlet has, for example, a connecting piece which is rigidly and tightly connected to the wall of the housing and which projects into the interior enclosed by the wall of the housing. The catalyst means can then be rigidly attached to the end of the connecting piece belonging to the inlet located in the interior of the housing. Furthermore, there may be an outlet, for example, which likewise has a stub, which is rigidly and tightly attached to the wall of the housing and projects into the interior thereof, provided in the latter with a perforation, to which the catalyst means are attached. The latter can then be spaced on all sides from the wall of the housing. These configurations of the catalytic converter, together with the design of the catalytic means, help to ensure that the catalytic means rapidly reach a temperature during a cold start - that is to say if they are still at ambient temperature when starting an engine producing the exhaust gas - in at least one area adjacent to the internal cavity be heated, which enables an effective catalytic treatment of the exhaust gas.

The catalytic means are preferably fastened in the housing without an intermediate layer between them and an inner surface of the wall of the housing, heat and sound-insulating, consisting of at least one non-metallic material and / or having a wire mesh. This contributes to the inexpensive manufacture of the catalyst.

The passages of the catalyst means are preferred Cross-sectional areas essentially constant over their entire lengths. This can contribute to an optimal utilization of the catalytically active material and thus to an inexpensive manufacture of the catalyst.

As already described, each sheet metal element package has, for example, alternately successive, first sheet metal elements having elevations and second, essentially flat sheet metal elements, the first and second sheet metal elements abutting one another at the apex lines of the shafts. This design of the catalyst means makes it possible to achieve a high number of passes in a cut perpendicular to the shafts and passages per unit area of the cut surface. The cut surface through the passages belonging to the same group can, depending on the design of the latter, have at least one flat part and / or be at least partly curved. The catalyst means preferably have at least about 62 passes per square centimeter (ie, at least about 400 passes per square inch), or more preferably at least about 93 passes per square centimeter (ie, at least about 600 passes per square inch), or more preferably at least about 124 passes, in a cut perpendicular to the passes per square centimeter (ie, at least about 800 passes per square inch) or even at least about 186 passes per square centimeter (ie, at least about 1200 passes per square inch) and, for example, about 248 passes per square centimeter (ie, around 1600 passes per square inch).

The height of the waves or humps measured from wave vertex to wave vertex or from hump summit point to hump summit point is expediently at most 2 mm, preferably at most 1 mm, preferably at least 0.3 mm and for example approximately 0.5 mm. If the ridges are formed by waves, the wavelength is for example two to three times the wave height and for a wave height of approximately 0.5 mm is, for example, approximately 1.2 mm to 1.4 mm.

The catalyst means preferably have holding means which hold the sheet metal elements together and connect them to one another. Each sheet metal element preferably has at least one flat holding section and, for example, at least two such. Each holding section is preferably rigidly connected to at least one element of the holding means and / or held by this at a distance from the holding section of another sheet metal element. The holding sections can, for example, be rigidly connected to spacer elements individually and / or in pairs by welding and / or brazing and / or clamping connections. This results in a stable connection of the sheet metal elements.

The sheet metal elements have, for example, an inner region or core region made of a metallic material, namely of a steel which, in addition to iron, contains approximately 20% by weight of chromium, approximately 5% by weight of aluminum and possibly also a little lanthanum and / or yttrium. The main sections of the sheet metal elements adjacent to the passages preferably have a coating of a metal oxide, namely aluminum oxide, which is often referred to as a "wash coat" and to which a catalytically active material is applied. This can have at least one noble metal, such as platinum and / or rhodium. The holding sections of the sheet metal elements are preferably bare and free of coatings, so that their surfaces are made of the same material as the inner areas or core areas of the sheet metal elements, i.e. are made of steel.

• die Fig. 1 einen Längsschnitt durch einen Katalysator, dessen Katalysatormittel zwei V-förmig angeordnete Katalysator-Körper mit je einer Gruppe von Durchgängen besitzen,
• die Fig. 2 einen Längsschnitt entlang der Linie II - II der Fig. 1 durch den in der letzteren ersichtlichen Katalysator,
• die Fig. 3 einen Querschnitt entlang der Linie III - III der Fig. 1 durch den in dieser ersichtlichen Katalysator,
• die Fig. 4 eine Schrägansicht von einem Katalysator-Körper der Katalysatormittel des in den Fig. 1 bis 3 gezeichneten Katalysators,
• die Fig. 5 einen Längsschnitt durch einen Katalysator mit zwei zueinander parallelen Katalysator-Körpern,
• die Fig. 6 einen Querschnitt entlang der Linie VI - VI der Fig. 5 durch den in dieser gezeichneten Katalysator,
• die Fig. 7 einen Längsschnitt durch einen anderen Katalysator, dessen Katalysatormittel zwei Gruppen von Durchgängen aufweisen,
• die Fig. 8 einen Schnitt entlang der Linie VIII - VIII der Fig. 7 durch den in dieser gezeichneten Katalysator,
• die Fig. 9 einen Schnitt entlang der Linie IX - IX der Fig. 7 durch den in dieser gezeichneten Katalysator,
• die Fig. 10 einen der Fig. 8 entsprechenden Schnitt durch einen anderen Katalysator,
• die Fig. 11 einen Längsschnitt durch einen anderen Katalysator,
• die Fig. 12 eine vereinfachte Schrägansicht des Katalysators gemäss der Fig. 11, wobei vom Gehäuse nur der Umriss des Mantels angedeutet ist,
• die Fig. 13 eine Schrägansicht von Teilen eines Katalysators, dessen Katalysatormittel drei Gruppen von Durchgängen besitzen,
• die Fig. 14 eine Schrägansicht von Teilen eines Katalysators mit Katalysatormitteln, die vier Gruppen von Durchgängen besitzen,
• die Fig. 15 einen Längsschnitt durch noch einen anderen Katalysator,
• die Fig. 16 eine vereinfachte Schrägansicht der Katalysatormittel des in der Fig. 15 gezeichneten Katalysators,
• die Fig. 17 eine Ansicht der Katalysatormittel gemäss der Fig. 16 in der in dieser durch den Pfeil XVII bezeichneten Blickrichtung, wobei auch noch der Mantel des Gehäuses dargestellt ist,
• die Fig. 18 einen Querschnitt durch die in den Figuren 15 bis 17 ersichtlichen Katalysatormittel,
• die Fig. 19 eine Ansicht der in den Figuren 15 bis 18 ersichtlichen Katalysatormittel in der in der Fig. 16 durch den Pfeil XIX bezeichneten Blickrichtung,
• die Fig. 20 eine Ansicht von Katalysatormitteln mit Blechelementen, die Buckel besitzen, und die Fig. 21 einen Schnitt entlang der Linie XXI - XXI der Fig. 20 in grösserem Massstab.

The subject matter of the invention is then explained with reference to exemplary embodiments shown in the drawing. In the drawing shows

• 1 shows a longitudinal section through a catalyst, the catalyst means of which have two V-shaped catalyst bodies, each with a group of passages,
• 2 shows a longitudinal section along the line II - II of FIG. 1 through the catalyst shown in the latter,
• 3 shows a cross section along the line III - III of FIG. 1 through the catalyst shown in this,
• 4 is an oblique view of a catalyst body of the catalyst means of the catalyst shown in FIGS. 1 to 3,
• 5 shows a longitudinal section through a catalytic converter with two mutually parallel catalyst bodies,
• 6 shows a cross section along the line VI - VI of FIG. 5 through the catalyst drawn therein,
• 7 shows a longitudinal section through another catalyst, the catalyst means of which have two groups of passages,
• 8 shows a section along the line VIII-VIII of FIG. 7 through the catalyst drawn therein,
• 9 shows a section along the line IX - IX of FIG. 7 through the catalyst drawn therein,
• 10 is a section corresponding to FIG. 8 through another catalyst,
• 11 is a longitudinal section through another catalyst,
• FIG. 12 shows a simplified oblique view of the catalytic converter according to FIG. 11, only the outline of the casing being indicated by the housing, FIG.
• 13 is an oblique view of parts of a catalyst whose catalyst means have three groups of passages,
• 14 is an oblique view of parts of a catalyst with catalyst means having four groups of passages,
• 15 shows a longitudinal section through yet another catalyst,
• 16 is a simplified oblique view of the catalyst means of the catalyst shown in FIG. 15,
• 17 is a view of the catalyst means according to FIG. 16 in the direction of view indicated by arrow XVII in this, the shell of the housing also being shown,
• 18 shows a cross section through the catalyst means shown in FIGS. 15 to 17,
• 19 is a view of the catalyst means shown in FIGS. 15 to 18 in the viewing direction indicated by the arrow XIX in FIG. 16,
• 20 shows a view of catalyst means with sheet metal elements which have humps, and FIG. 21 shows a section along the line XXI-XXI of FIG. 20 on a larger scale.

It should also be noted that various figures are quite schematic and some are not to scale.

The catalytic converter 201 shown in FIGS. 1 to 3 defines an axis 202 and has a housing 203. Its wall has a casing 204, a first end wall 205 and a second end wall 206. The casing 204 encloses the axis 202, runs along it and is essentially parallel to it. The jacket 204 is formed, for example, from a piece of sheet metal, the edges of which are parallel to the axis and are firmly and tightly connected to one another by a flange shown in FIG. 3. The edges of the end walls 205, 206 are also connected, for example, to the edges of the jacket 204 by flanges.

The jacket 204 is substantially rectangular in a cross section perpendicular to the axis, but the corners of the rectangle are replaced by curved transitions. The jacket thus forms two first, opposing side and / or longitudinal walls 204a and two second, opposing side and / or longitudinal walls 204b. The four side and / or longitudinal walls belonging to the jacket are essentially - i.e. apart from the mentioned curved transitions and apart from the flanges - even and in pairs parallel to each other. The housing 203 has a central plane running between the two first side and / or longitudinal walls 204a and through the axis 202 and perpendicular to the walls 204b, identical to the sectional plane of FIG. 2 and designated 209 in FIG. 3. The housing 203 and its casing have a first cross-sectional dimension measured at right angles to this central plane 209 and a second cross-sectional dimension measured parallel to the named central plane, which is smaller than the first cross-sectional dimension.

The end walls 205, 206 are substantially flat and perpendicular to the axis 202 and have the cross-sectional shape of the Coat corresponding outline shapes. The first end wall 205 has a first opening 205a. The second end wall 206 has a second opening 206a. A nozzle is attached to each end wall, namely welded into a collar delimiting the opening 205a or 206a. Each nozzle has an outer, cylindrical section and a section widening away from it towards the interior of the housing. The two openings 205a, 206a together with the connecting pieces form the inlet 207 and the outlet 208 of the catalytic converter. Inlet 207 and outlet 207 are coaxial with axis 202.

The housing 203 contains catalyst means 210 with two catalyst bodies 211, one of which is shown separately in FIG. 4. Each catalyst body 211 has essentially the shape of a prism and has six essentially flat surfaces or, as will be explained below, at least flat lubrication surfaces, namely a base surface 211a, a cover surface 211b parallel to this, an outer surface 211c, one parallel to this Inner surface 211d, a first end surface 211e and a second end surface 211f parallel thereto. In the section drawn in FIG. 1, the two prism-shaped catalyst bodies 211, like their base surfaces 211a and cover surfaces 211b, have the shape of an oblique-angled parallelogram with edges of different lengths. The outer and inner surfaces 211c and 211d are rectangular and each connect a longer edge of the base surface with a longer edge of the top surface. The two end surfaces 211e, 211f each connect a shorter edge of the base surface with a shorter edge of the cover surface.

Each catalytic converter body 211 has a package of alternately successive first sheet metal elements 213 and second sheet metal elements 214. Furthermore, each catalytic converter body has the holding means holding the sheet metal elements together with spacer elements 215. Each sheet metal element and holding element consists, for example, of a separate workpiece. The In a plan view, sheet metal elements 213, 214 have the same outline shapes as the base area 211a and the top area 211b of a catalytic converter body 211 and thus form an oblique-angled parallelogram.

Each first sheet metal element 213 has a main section 213a, which is provided with shafts 213b which extend parallel to one another and parallel to the end surfaces 211e, 211f from the outer surface 211c to the inner surface 211d. The shaft crests 213c and 213d of the shafts 213b of each first sheet metal element 213 define two flat, parallel to the base surface 211a and top surface 211b sliding surfaces. Accordingly, all of the flat sliding surfaces defined by first sheet metal elements are parallel to one another. The wave height of the waves measured from vertex to vertex is preferably at least 0.3 mm and for example 0.5 mm to 1 mm. The wavelength can be at least equal to the wave height, for example. Each first sheet metal element 213 has on its sides of its main section 213a facing away from one another and namely at the end surfaces 211e, 211f along the shafts, parallel, strip-shaped, flat holding sections 213e and 213f.

Every second sheet metal element 214 is at least substantially flat. The base area 211a and the cover area 211b of the catalyst body 211 can each be formed, for example, by a second sheet metal element 214. Every second sheet metal element 214 has a main section 214a which, in the case of the second sheet metal elements which form the base or top surface of the catalyst body, bears against the wave apexes of an adjacent first sheet metal element 213 and for all other second sheet metal elements against wave apices of two adjacent first sheet metal elements 213. Every second sheet metal element 214 has a strip-shaped, of course also flat holding section 214e or 214f on sides of its main section 214a facing away from one another.

Each spacer element 215 consists of a straight piece of a profile bar which is square in cross section. If one disregards the sheet metal elements that form the base area and cover area of the catalyst body, the holding sections 213e, 213f, 214e, 214f of the first and second sheet metal elements 213, 214 lie directly against one another in pairs. The spacer elements 215 extend over the entire length of the shafts and are arranged between two holding sections 213e and 214e or 213f and 214f.

The sheet metal elements 213, 214 consist for example of the steel mentioned in the introduction. The two mutually facing surfaces of the main section 213a, 214a of each sheet metal element 213, 214 are provided with an aluminum oxide coating. Catalytically active material, which has, for example, platinum and / or rhodium, is applied to the aluminum oxide coatings. The holding sections 213e, 213f, 214e, 214f of the sheet metal elements are preferably bare and uncoated, so that their surfaces are made of steel. The spacer elements 215 likewise consist of a metallic material - namely steel - and may also be provided with coatings made of aluminum oxide and catalytically active material on their surfaces facing the shafts 213b.

The mutually abutting holding sections 213e, 214e, 213f, 214f and spacer elements 215 are rigidly connected to one another, namely welded. The abutting main sections of the sheet metal elements 213, 214 together delimit passages 217 which, like the shafts 213b, extend from the outer surface 211c to the inner surface 211d. The two surfaces 211c, 211d thus form the outer or the inner mouth surface of the passages. Each catalyst body 211 thus has a group of straight passages 217 which are parallel to one another and to the surfaces 211a, 211b, 211e, 211f and run between these surfaces. Each passage 217 has a cross-sectional area that is constant over its entire length. Apart from the passages adjoining the spacer elements 215, all passages also have cross-sectional areas of the same size. Furthermore, all runs are of equal length.

As already mentioned, the base surface 211a and the cover surface 211b of each essentially prism-shaped catalyst body 211 are each formed, for example, by a second sheet metal element 214 and are accordingly essentially flat. However, it would also be possible for at least one of the most distant sheet metal elements of each catalyst body 211 to consist of a second corrugated sheet metal element. If this should be the case, the base area and / or cover area of the catalytic converter is understood to mean the flat lubricating surface that clings to the outer shaft apex of the relevant outermost sheet metal element.

The base surface 211a and the top surface 211b of each catalytic converter body 211 face one of the second side and / or longitudinal walls 204b and - in the sense explained above - are essentially flat and parallel to the second side or longitudinal walls 204b. The two catalyst bodies 211 lie on their base surfaces 211a and cover surfaces 211b, for example according to FIGS. 2 and 3, each on one of the two second, wider side and / or longitudinal walls 204b of the housing 203.

The surfaces 211c, 211d, 211e, 211f of the two catalyst bodies 211 are perpendicular to the base surface 211a, to the cover surface 211b and to the second, wider side and / or longitudinal walls 204b of the housing. The first outer surface 211c and the first end surface 211e together form an angle designated by alpha in FIG. 4, which angle differs from 90 °, is at least 45 °, preferably at least 60 ° and, for example, 75 ° to 87 °.

The first and second end surfaces 211e of the two catalyst bodies 211 are tightly fastened, for example welded, to regions of the end wall 205 which are located in FIG. 1 on opposite sides of the axis 202 and the mouth opening of the inlet 207. The outer surfaces 211c of the two catalyst bodies 211 face away from one another and face one of the first side and / or longitudinal walls 204a. The two inner surfaces 211d of the two catalyst bodies face one another and approach one another in the direction running away from the inlet 207. The surfaces 211c, 211d form an angle with the central plane 209 running through the axis 202, which is equal to the difference 90 ° - alpha and therefore at most 45 °, preferably at most 30 ° and for example 3 ° to 15 °. The two catalyst bodies 211 are tightly and firmly connected to one another at their end faces 211f facing away from the inlet 207, for example welded directly and / or via a connecting element connecting them. In the section shown in FIG. 1, the two catalyst bodies thus together form a V and are mirror-symmetrical to one another with respect to the central plane 209 running between them.

The mentioned first and second cross-sectional dimensions of the jacket 204 and also the maximum cross-sectional dimension measured between diagonally opposite corners of the jacket 204 and the entire housing are smaller than the length of the jacket 204. Likewise, the cross-sectional dimensions of the catalyst means measured analogously at right angles to the axis 202 210 all less than the length of the catalyst means 210 measured parallel to the axis 202.

The interior or passage of the inlet 207 opens at the first opening 205a of the housing 203 into an inner cavity 221, which is present in the latter between the inner surfaces 211d of the two catalyst bodies 211 and is polygonal in cross-section, namely quadrangular in shape Inlet 207 has at its mouth opening into the inner cavity 221 essentially, ie at least approximately and preferably exactly the same polygonal, namely square-shaped outline or cross-sectional shape and essentially, ie at least approximately and preferably exactly the same outline or cross-sectional dimensions as that End of the inner cavity 221 closer to the inlet. This contains no solid parts, that is to say is completely free and becomes narrower in the direction in FIG. 1 along the axis 202 in the direction away from the inlet. The width and cross-sectional area of the inner cavity 221 decrease linearly away from the inlet 207, so that at the inner ends furthest from the inlet, the passages 247 almost decrease to zero, ie practically disappear.

The two groups of passages 217 formed by the catalyst bodies are perpendicular to the central plane 209 and run on sides facing away from one another and away from the inner cavity 221. Furthermore, the two groups of passages 217 at the outer passage ends opening into the outer cavity 222 are at a distance from one another which is very much greater than the distance from adjacent ones, i.e. passages belonging to the same catalyst body.

Gaps exist between the inner surfaces of the first side or longitudinal walls 204a of the housing and the first side surfaces 211c of the catalytic converter body facing them, together with a space present between the inner surface of the end wall 206 of the housing and the end surfaces 211f of the catalytic converter body form an outer cavity 222 which is connected to the interior of the outlet 208 at the second end wall 206 of the housing. The mouth opening of the interior or passage of the outlet 208 opening into the outer cavity 222 can be circular or, like the mouth opening of the inlet 207, square.

For its use, the catalytic converter 201 can be installed, for example, in a line of an exhaust device of the gasoline internal combustion engine of an automobile and can be arranged under the bottom thereof in such a way that the second, wider side and / or longitudinal walls 204b of the housing are approximately parallel to the bottom of the automobile and to the surface on which it stands or drives. The catalytic converter 201 then only requires a small height because of its relatively flat shape.

During operation of the catalytic converter 201, an exhaust gas flow represented by arrows in FIG. 1 arises. The exhaust gas flows through the inlet 207 into the inner cavity 221, is deflected into the latter and flows into the inner ends of the passages 217 at the inner surfaces 211d serving as exhaust gas entry surfaces. The exhaust gas is treated catalytically as it flows through the passages, emerges again from the catalyst bodies at the outer surfaces 211c serving as exhaust gas exit surfaces and then flows through the outer cavity 222 to the outlet.

The inclination of the inner surfaces 211d against the axis 202 and the resulting decrease in the cross-sectional area of the inner cavity with increasing distance from the inlet contribute to the fact that the exhaust gas flow as it flows into the catalyst body is uniform over the whole, relatively large, as exhaust gas -Interior surface serving inner surfaces 211d and is accordingly evenly distributed over all passages 217. This makes it possible to achieve a high degree of efficiency in the catalytic treatment and to keep the pressure loss or counterpressure caused by the catalyst low.

The exhaust gas can flow between the mouth of the inlet 207 formed by the first opening 205a and the outer surfaces 211d serving as exhaust gas entry surfaces of the catalytic converter body only come into contact with relatively small areas of the walls of the housing 203. Accordingly, the exhaust gas can only give off a little heat to the surroundings via the housing wall between the inlet and the exhaust gas inlet surfaces of the catalyst bodies. The two catalyst bodies also give off heat to the environment only relatively slowly via the housing wall. In the event of a cold start, therefore, at least the regions of the catalyst bodies 211 adjoining the inner cavity 221 are quickly heated by the exhaust gas to a temperature which enables effective catalytic treatment of the exhaust gas.

The catalyst 231 shown in FIGS. 5 and 6 defines an axis 232 and has a housing 233 with a jacket 234. This has two first side and / or longitudinal walls 234a and two second side and / or longitudinal walls 234b. The jacket 234 is again essentially rectangular in cross section, so that the side and / or longitudinal walls are essentially flat and in pairs parallel to one another. Furthermore, the first side and / or longitudinal walls 234a are narrower than the second side and / or longitudinal walls 234b. The housing has a first end wall 235 with a first opening 235a and a second end wall 236 with a second opening 236a. The two openings together with connecting pieces welded into them form an inlet 237 or an outlet 238. In FIG. 6, a central plane 239 running through the axis 232 between the two walls 234a is drawn.

The housing contains catalyst means 240 with two catalyst bodies 241 which are arranged on mutually facing sides of the central plane 239 and are symmetrical with respect to this. Each catalyst body 241 has a base surface 241a, a top surface 241b, an outer surface 241c, an inner surface 241d, a first end surface 241e and a second end surface 241f. In the section shown in FIG. 5, the two catalyst bodies 241 form a parallelogram with one another right-angled sides, namely a rectangle. Accordingly, the base area 241a and the top area 241b of each catalyst body 241 form a rectangle. The surfaces 241c, 241d, 241e, 241f are perpendicular to the base surface 241a and to the top surface 241b. Each catalyst body 241 thus essentially forms a cuboid prism.

Apart from the other shapes of their base and cover surfaces, the two catalyst bodies 241 are, for example, of a similar design to the catalyst bodies 211. They have in particular first sheet metal elements provided with waves and second, essentially flat sheet metal elements.

The various sheet metal elements of the catalytic converter body 241 then form a right-angled parallelogram, namely a rectangle, in plan view and can, for example, as with the catalytic converter body 211, each consist of a separate sheet metal piece and be welded to one another and with spacer elements. However, the sheet metal elements belonging to the same catalytic converter body can also be formed by sections of a one-piece, folded sheet metal strip and alternately connected by a fold at the first or second end face. Furthermore, each catalytic converter body 241 has a group of straight passages 247, which are parallel to one another and run perpendicular to the inner surface 241d, from the latter to the outer surface 241c.

Each base and top surface 241a, 241b of the two catalyst bodies 241 faces one of the second, wider side or longitudinal walls 243b and bears against one of these walls. The two catalyst bodies 241 rest at their first end faces 241e on opposite sides of the first opening 235a against the first end wall 235 and are connected to the first end wall 235, for example, by welded connections. The surfaces 241c, 241d of the two catalyst bodies 241 are parallel to one another and to the central plane 239. The passages 247 are accordingly perpendicular to the central plane 239. The outer surfaces 241c of the two catalyst bodies are each spaced from one of the first, narrower side and / or longitudinal walls 234a and are parallel to these walls 234a. The inner surfaces 241d of the two catalyst bodies are parallel to one another and are spaced apart over their entire lengths. The two second end faces 241f of the catalytic converter body facing away from the first end wall 235 are tightly and firmly connected, for example welded, to an end and / or end element 249 which is formed from a rectangular disk and is at a distance from the second end wall 236. The two catalyst bodies 241 and the two groups of passages 247 which they form are at a distance from one another which is very much greater than the distance from adjacent passages which are present in the same catalyst body.

A preferably hollow limiting element 250 inserted between the two catalyst bodies 241 has a square, rectangular or square-shaped end 250a in cross section, which is tight and tight with the end and / or end wall 249 and / or directly with the ends facing away from the inlet the catalyst body 241 is connected, for example welded. The width of the end 250a of the limiting element 250 measured parallel to the passages 247 is almost or exactly the same as the distance between the mutually facing inner surfaces 241d of the two catalyst bodies. The limiting element 250 protrudes between the two catalyst bodies 241 to approximately the mouth of the inlet 237. At the mouth of the inlet, the limiting element has a cutting-like or possibly a little rounded end, the edge or apex line of which lies in the middle plane mentioned, which lies between the both walls 234a and between the two catalyst bodies 241 through the axis 232. The boundary element 250 has two boundary surfaces facing away from one another 250b, each of which faces an inner surface 241d in front of one of the catalyst bodies 241. The two boundary surfaces 250b are inclined toward one another away from the inlet 237 along the axis 232, so that each boundary surface approaches the inner surface 241d of a catalytic converter body 241 opposite it from the inlet. The boundary surfaces 250b are flat and form an angle with the axis 232, the central plane running between them and the inner surfaces 241d which is at most 45 °, preferably at most 30 ° and for example at most 15 °. The limiting element 250 also has two surfaces 250c which are parallel to one another and to the second side or longitudinal walls 234b of the housing, each of which faces one of the second side or longitudinal walls 234b and bears against the latter.

The interior of the inlet 237 opens into an inner cavity 251 present between the two catalyst bodies 241. The limiting element 250 divides the inner cavity 251 at least for the most part from its axial extent into two free areas, the widths and cross-sectional areas of which along the axis 232 Decrease linearly from inlet 237 and become almost zero on the farthest passages. Between the first side or longitudinal walls 234a and the end wall 236 of the housing 234 and the first side surfaces 241c of the catalytic converter body and the end wall 249 there is an outer cavity 252 which is connected to the interior of the outlet 238.

When the catalytic converter 241 is operating, the exhaust gas flows through the inlet 237 into the inner cavity 251 which is divided into two free areas by the limiting element 250. The exhaust gas is deflected in these free areas of the inner cavity 251 and flows in the areas adjacent to the free cavity areas, inner surfaces parallel to axis 232 241d the catalyst body 241 in their passages 247. The deflection of the exhaust gas in the inner cavity 251 is supported by the boundary surfaces 250b inclined away from the inlet 237 against the inner surfaces 241d serving as exhaust gas entry surfaces. The exhaust gas then flows out through the passages 247 into the outer cavity 252 and through this to the outlet.

Unless otherwise stated above, the catalytic converter 231 is configured similarly to the catalytic converter 201 and has properties similar to this.

The catalytic converter 261 shown in FIGS. 7 to 9 has an axis 262 and a housing 263 with a jacket 264 enclosing the axis 262. This has two first, in cross-section, for example, arcuate side and / or longitudinal walls 264a and two second, for example flat and parallel longitudinal walls 264b. The jacket is connected at its ends to a first end wall 265 and a second end wall 266, respectively. The two end walls have an opening 265a and 266a, which is coaxial to the axis 262 and into which a connecting piece serving as inlet 267 and outlet 268 is welded. The housing defines a central plane 269 extending between the walls 264a and through the axis 262 and has a first cross-sectional dimension measured at right angles to this and a second cross-sectional dimension measured parallel to the central plane 269, which in turn is smaller than the first cross-sectional dimension.

The catalyst means 270 arranged in the housing have two catalyst bodies 271. These are mirror-symmetrical with respect to the central plane 269. The two catalyst bodies 271 have essentially flat abutting base surfaces 271a and flat, abutting abutment surfaces 271b or a common, coherent base surface 271a and a common, coherent top surface 271b. Each catalyst body 271 also has an outer surface 271c, an inner surface 271d, a first end surface 271c and a second end surface 271f. The surfaces 271a, 271b are parallel to one another and to the walls 264b and bear against them. The two inner surfaces 271d are curved control surfaces in cross section and abut one another at their longitudinal edges parallel to the axis 262. The edges of the two inner surfaces 271d which are closer to the inlet 267 and can be seen in FIG. 8 together form a self-contained line, namely a circle. The two inner surfaces 271d are thus at their end located at the inlet 267 at their central cross-sectional areas - ie with the exception of their abutting longitudinal edges - at a distance from one another. The central cross-sectional areas of the two inner surfaces 271c approach each other in the direction extending away from the inlet 267 in such a way that their ends, which are further away from the inlet, have straight, substantially coincident edges lying in the central plane 269. In the cross section located between the two ends of the catalyst body and drawn in FIG. 9, the two inner surfaces 271d are together lenticular. The two outer surfaces 271c are also curved control surfaces in cross section. Each outer surface 271c is at least approximately parallel to the inner surface 271d of the catalyst body 271 in question in all the cuts parallel to the axis 262 and perpendicular to the central plane 269.

Each catalytic converter body 271 is formed from a package of at least originally rectangular, alternately successive, first and second sheet metal elements. The first sheet metal elements have shafts, some of which are indicated in FIG. 7. The waves run at right angles to the longitudinal edges of the first sheet metal elements. The second sheet metal elements are essentially flat. The first and second sheet metal elements are rotated against one another in this way during the production of the catalyst bodies 271 stacked on top of one another and rigidly connected to one another by holding means with spacer elements arranged at the ends of the catalytic converter body, such that the outer and the inner longitudinal edges of the sheet metal elements together form the outer surfaces 271c and the inner surfaces 271d of the catalytic converter body. If the sheet metal elements of the finished catalyst bodies remain exactly rectangular, the end surfaces 271e, 271f form curved control surfaces. However, the first end surfaces 271e can be formed, for example, at least in their regions which abut the inner surfaces 271d in a flat manner and parallel to the first end wall 265, against which they rest in the finished catalytic converter 261. The two catalyst bodies 271 are rigidly and tightly connected to one another, for example welded. Furthermore, the two catalyst bodies are connected to the housing 263, for example welded. In particular, the first end faces 271e of the catalyst body are tightly connected to the first end wall 265 of the housing.

Each catalyst body 271 has a group of straight passages 277 that run from the inner surface 271d to the outer surface 271c. All passages 277 are parallel to the second side and / or longitudinal walls 264b and thus also to one and the same plane. Furthermore, all the passages formed by the same pair of sheet metal elements are parallel to each other. In contrast, the passages form angles with the central plane 269, the value of which depends on the distance from the plane running at right angles to the central plane 269 through the axis 262 and through the centers of the catalyst bodies. In the case of the passages closest to the base surface 271a or the cover surface 271b, the said angle is at least approximately 90 °. 7, the passages 277 with the central plane 269 then form an angle deviating from 90 °, preferably at least 45 ° and, for example, at least 60 °. The passages 277 are one along their entire length constant cross-sectional area. Furthermore, all the passages 277 are at least approximately the same length.

The inlet 267 opens into an inner, free cavity 281 enclosed by the two inner surfaces 271d. The opening of the inlet opening into the inner cavity is circular and has approximately the same diameter as the end of the inner cavity 281 located at the first end wall 265 The cross-sectional area of the inner cavity 281 decreases linearly with the distance from the inlet in the direction extending from the inlet in accordance with the formation of the inner surfaces 271d. An outer cavity 282 connected to the outlet 268 is present between the outer surfaces 271c and the second end surfaces 271f and the walls 264a, 266 of the housing. In the case of the catalyst 261, the inner mouth surfaces of the two groups of passages formed by the inner surfaces 271d abut one another. In the remaining parts of the passages, and in particular in their outer ends opening into the outer surfaces 271c, the two groups of passages are in turn spaced apart.

When the catalytic converter 261 is operating, exhaust gas is introduced into the inner cavity 281 through the inlet 267, enters the passages 277 of the two catalytic converter bodies 271 at the internal surfaces 271d serving as exhaust gas entry surfaces, flows through the external surfaces 271c serving as exhaust gas exit surfaces again out of the catalyst bodies and then flows through the outer cavity 282 to the outlet 268. Since the inner cavity 281 of the catalyst 261 is essentially completely and exclusively delimited by the inner surfaces 271d of the catalyst body 271, the exhaust gas can flow between the outflows emit even less heat from the inlet and the inflow into the catalytic converter body to the surroundings of the catalytic converter 261 than in the previously described catalytic converters 201 and 231. Accordingly, the In the case of a cold start, the catalyst body 271 is heated to the operating temperature required for the catalytic treatment of the exhaust gas even more quickly than in the case of the catalysts 201 and 231.

The catalyst 291 shown in FIG. 10 has a housing 293 with a jacket 294 and catalyst means 295 arranged in the housing. The catalyst 291 is largely similar to the catalyst 261 shown in FIGS. 7 to 9, but differs from it in this way that between the jacket 294 and the catalyst means 295 there is an outer cavity 297 which completely surrounds this in cross section.

The catalytic converter 301 shown in FIGS. 11 and 12 has an axis 302 and a housing 303. This is of similar design to the housing 263 and has a jacket 304, end walls 305 and 306, an inlet 307 and an outlet 308. The housing 303 contains catalyst means 310 with two catalyst bodies 311 arranged on different sides of a central plane of the housing. These have a base area 311a, a cover area 311b, an outer area 311c, an inner area 311d and two end areas 311e, 311f. The inner surfaces 311d are parallel to the axis 302 and together form an approximately circular cylindrical surface in cross section. The outer surfaces 311c are also parallel to the axis 302 and bent in cross section in such a way that the distances of the outer surface 311c from the inner surface 311d of the catalyst body in question, measured at right angles to the median plane, are the same everywhere. The end faces 311e and 311f of the catalytic converter body are flat and perpendicular to the axis 302. Each catalytic converter body 311 has first sheet metal elements with waves shown in part in FIGS. 11 and 12 as well as second, essentially flat sheet metal elements. Each catalytic converter body has a group of straight lines, perpendicular to the median plane mentioned Inner surface 311d extending to outer surface 311c and having substantially the same length of passages 317.

The two catalyst bodies 311 are rigid and tightly connected to one another and to the end wall 305. A disc-shaped end and / or end element 319 is attached to the end of the catalyst body 311 facing away from this. This holds a limiting element 320 which projects into the inner cavity 321 enclosed by the inner surfaces 311d up to approximately the mouth of the inlet. The delimiting element 320 is, for example, hollow, rotationally symmetrical to the axis 302 and approximately paraboloid-shaped and has a delimiting surface 320a on the outside. Together with the inner surfaces 311d of the two catalytic converter bodies 311, this delimits a free area of the inner cavity 321 which is annular in cross section. The cross sectional area of this free area of the inner cavity 321 decreases linearly away from the inlet 307, so that it corresponds to the inner ends of the most distant passages 317 is almost zero. The outer ends of the passages 317 open into an outer cavity 322 which is connected to the outlet 308.

Unless otherwise stated above, the catalyst 301 is configured similarly to the catalyst 261.

The catalytic converter 361, which is partly shown in FIG. 13, defines an axis 363 and has a housing 363, of which only the outline of the jacket 364 surrounding the axis 362 is indicated. This has three flat side and / or longitudinal walls 364a distributed around the axis and defines an equilateral triangle in cross section, but the corners of the triangle are replaced by side and / or longitudinal walls 364b curved in cross section.

The housing 363 contains catalyst means 370 with three distributed around the axis 362 against the curved walls 364b protruding catalyst bodies 371. Each of these has two flat side surfaces 371a or 371b which are parallel to one another and to the axis 362, an outer surface 371c, an inner surface 371d and two end surfaces 371e or 371f. The outer surfaces 371c and inner surfaces 371d are curved in cross section and parallel to the axis 362. The three inner surfaces 371d together form a cylindrical surface with a circular cross section. The outer surfaces 371c, measured parallel to the side surfaces 371a, 371b of the catalyst body in question, are at least approximately the same distance from the inner surfaces 371d everywhere. The end surfaces 371e, 371f are substantially flat and perpendicular to the axis 362. Each catalyst body 371 has a package of rectangular, alternately successive, first and second sheet metal elements. The first sheet metal elements partially have shafts indicated in FIG. 13, while the second sheet metal elements are essentially flat and parallel to the axis 362. Each catalytic converter body has a group of straight passages 377 which extend parallel to a plane running through axis 362 and the relevant catalytic converter body and to one another from inner surface 371d to outer surface 371c, perpendicular to one which runs through axis 362 Inner surface 371d of the relevant catalyst body are opposite plane, have a constant cross-sectional area over their entire length and are all at least approximately the same length.

The three catalytic converter bodies 371 enclose an approximately paraboloid-shaped limiting element 380. Together with the inner surfaces 371d, the catalytic converter body 371 delimits a free area of annular cross-section of an inner cavity 381, which is completely enclosed in cross-section by the inner surfaces 371d, into which the non- drawn inlet opens and its cross-sectional area decreases away from the inlet. The outside of the jacket 364 and the surfaces 371a, 371b, 371c of the catalyst body 371 Cavity 382 is connected to the not shown outlet of the housing. The three groups of passages 377 thus extend in three different directions from the inner cavity 381 to the outer cavity 382 and are spaced apart from one another everywhere except for the inner ends of the passages.

The catalytic converter 401 shown in FIG. 14 defines an axis 402 and has a housing 403, of which only the jacket 404 is indicated. This has, for example, four flat walls distributed around the axis and four walls curved in cross section, but instead could be curved everywhere in cross section and be more or less circular.

The housing 403 contains catalyst means 410 with four catalyst bodies 411. These are evenly distributed around the axis 362 and together form a cross. The catalyst bodies 411 are configured similarly to the catalyst bodies 371 and in particular each have an outer surface 411c and an inner surface 411d. Each catalytic converter body 411 in turn has a package of sheet metal elements and a group of straight passages 417 running parallel to one another and extending from the inner surface 411d to the outer surface 411c. The inner surfaces 411d together form a closed cylindrical surface and enclose a paraboloid-shaped delimiting element 420 and an inner cavity 421 with an annular free area, the cross-sectional area of which decreases away from the inlet opening into it, not shown. An outer cavity 422, which is connected to the outlet (not shown), is present between the jacket 404 and the outer surfaces 411c.

The catalytic converter 431 shown schematically in FIG. 15 defines an axis 432 and has a housing 433 with a metallic wall. This points one to the axis 432 parallel jacket 434 and at its two ends arranged, tightly and tightly connected by flanges with this end walls 435, 436. The jacket is also indicated in FIG. 17 and, according to this, has approximately the shape of a square in cross section, the corners of which are replaced by rounded transitions. The two end walls 435, 436 are substantially flat and perpendicular to the axis 432 and have a hole in the center. The inlet 437 and the outlet 438 of the catalytic converter 431 each have a connection piece, which consists of a cylindrical tube piece, penetrates the hole in the first end wall 435 and the second end wall 436, projects into the interior enclosed by the wall of the housing and is rigid and tight connected to the relevant end wall, namely welded. The section of the nozzle or pipe piece belonging to the outlet 438, which is located in the interior, is provided with holes 438a distributed over its jacket.

The catalytic converter 431 has catalytic converter means 440 arranged in the housing and also visible in FIGS. 16, 17, 18, 19, with four catalytic converter bodies 441 distributed around the axis 432 and forming a cross. Each of these has two flat side surfaces 441a and 441b parallel to one another and to the axis 432, an outer surface 441c and an inner surface 441d with two end surfaces 441e and 441f. The four inner surfaces 441d together form a surface that completely surrounds the axis. In contrast, the outer surfaces 441c of the four catalyst bodies 441 are at a distance from one another. The edges of the inner surfaces 441d which abut the end surfaces 441e and can be seen in FIGS. 15 and 16 together form a self-contained line, namely essentially a circle. The outer surfaces 441c and inner surfaces 441d consist of control surfaces and are straight and parallel to each other in all sections parallel to the side surfaces 441a, 441b of each catalyst body 441. The longitudinal edges of the outer surfaces 441c and the four inner surfaces 441d are also parallel to axis 432 and abut each other in pairs. The remaining, central cross-sectional areas of the outer and inner surfaces are inclined away from the end surfaces 441e towards the axis, so that the inner surfaces 441d of each catalyst body 441 have a V-shaped edge at the end surface 441f thereof, which is at the edge of each V-leg abuts an adjacent inner surface 441d. Accordingly, the four inner surfaces 441d converge at their edges abutting the end surfaces 441f to form two crossing straight lines.

Each catalytic converter body 441 has a package of alternately successive, first and second sheet metal elements. The first sheet metal elements 443 partly have shafts indicated in FIGS. 15 and 16. Each first sheet metal element 443 defines two planar lubricating surfaces that cling to its shaft apex. The second sheet metal elements are again essentially flat. The sheet metal elements are rectangular in a projection perpendicular to the planar lubricating surfaces of the first sheet metal elements 443 and to the surfaces and lubricating surfaces of the second sheet metal elements, so that in particular the two longer edges of each sheet metal element are straight and parallel to one another. The waves of each first sheet metal element 443 are straight, parallel to one another and perpendicular to the longitudinal edges of the sheet metal element in question. The sheet metal elements belonging to the same catalytic converter body 441 are rigidly connected to one another by holding means in such a way that the second, flat sheet metal elements bear against the shaft apices of the first sheet metal elements 443. The holding means can, for example, have strip-like or strip-shaped spacer elements 445, which, like the spacer elements 215 of the catalytic converter body shown in FIG. 4, are arranged at the shorter edges of the sheet metal elements and at least approximately parallel to waves of the first sheet metal element lying against them 443 run. However, the sheet metal elements belonging to the same catalytic converter body are twisted against one another in such a way that theirs Longitudinal edges together form the outer surface 441c and inner surface 441d, which each consist of a curved control surface. The sheet metal elements belonging to one and the same catalyst body 441 are welded to one another and to the spacer elements at their shorter edges. The end surfaces 441e, 441f can consist of curved control surfaces which result when the rectangular sheet-metal elements are rotated. However, end faces 441e are shown as planes in FIG. 16 for simplicity. However, end surfaces 441e and / or 441f could be made flat and perpendicular to axis 432 by post-processing. The four catalyst bodies 444 are rigidly and tightly connected to one another at the longitudinal edges of their inner surfaces 441d and at the edges of the inner surfaces 441d located in the end surfaces 441f, namely welded. If necessary, there may still be some struts or the like which are not shown and which additionally connect the various catalyst bodies to one another. Each catalyst body 441 has a group of straight passages 447 that run from the inner surface 441c to the outer surface 441d. All the passages 447 belonging to the same catalyst body 441 are parallel to one and the same plane running through the axis 432 and through the center of the catalyst body and to the side surfaces 441a, 441b. The passages 447 are also perpendicular to the longitudinal edges of the first sheet metal elements delimiting them. The passages 447 belonging to the same catalytic converter body 441 therefore have different directions which, analogously to the catalytic converter 261 shown in FIGS. 7 to 9, depend on the distance from the plane running through the axis 432 and through the center of the catalytic converter body 441 are. It should also be noted that each catalytic converter body 441 actually has much more sheet metal elements than its external dimensions than is shown in FIGS. 16 to 20.

The catalyst means 440 are at the end faces 441e, 441f rigidly connected to the ends of the connecting pieces which are located in the interior of the housing 433 and which form the inlet 437 and the outlet 438. The catalyst means 440 are spaced on all sides from the wall of the housing 433. The connection piece forming the inlet 437 opens at its end which is tightly connected to the four catalyst bodies 441 into the inner cavity 451 enclosed by the inner surfaces 441d. The one to the four catalyst Passages 447 belonging to bodies 441 run away from the inner cavity 451 in accordance with the arrangement of the catalyst bodies on four different sides of the inner cavity 451, which are evenly distributed around the axis 432. The inside diameter of the inlet 437 and in particular of its end connected to the catalyst means 440 is approximately and preferably exactly the same as the diameter of the circle formed by the edges of the inner surfaces 441d located in the end surfaces 441e, so that the inner cavity 451 is stepless connects to the interior of the inlet. The inner cavity 451 is completely free, that is to say does not contain any limiting element corresponding to the limiting elements 250, 380, 420 and has a cross-sectional area that decreases linearly along the axis 432 from the inlet. Between the jacket 434 and the surfaces 441a, 441b, 441c of the catalytic converter body 441 there is an outer cavity 452 which is connected to the interior thereof by the holes 438a of the nozzle of the outlet 438.

The catalytic converter 431 can be installed in an exhaust system of an internal combustion engine. During its operation, exhaust gas illustrated by arrows in FIG. 15 then flows through the inlet 437 into the inner cavity 451. The exhaust gas is deflected therein and distributed to the passages 447 and then flows through the passages 447, where it is catalytically treated. The exhaust gas then enters the outer cavity 452 and flows therein to the outlet 438, a portion of the exhaust gas also flowing between the side surfaces 441a, 441b of adjacent catalyst bodies 441 can. The exhaust gas then flows through the holes 438a into the interior of the outlet 438 and leaves the interior of the housing 433 through this.

The catalyst shown in FIGS. 15 to 19 has various advantages, some of which have already been described in the introduction and / or in relation to the catalysts shown in FIGS. 1 to 14, and combines these advantages in a particularly advantageous manner. For example, the catalytic converter 431 has only relatively small cross-sectional dimensions at right angles to the axis 432 compared to the amount of exhaust gas to be treated per unit of time. Furthermore, the passages 447 present in the catalyst bodies 441 can have small cross-sectional areas and be close to one another. Each catalyst body 441 can therefore have a large number of passages per unit area of its outer surface 441c or inner surface 441d perpendicular to the passages 447 or a curved cutting surface parallel to these surfaces or also per unit surface of a flat cutting surface perpendicular to at least a few passages. This in turn makes it possible to achieve a high degree of efficiency, to make the passages relatively short and to keep the volume, the weight and the precious metal requirement of the catalyst agents low. Because the passages 447 are relatively short compared to the amount of exhaust gas to be treated and compared to the axial expansion of the catalyst means and the length of the inner surfaces 441d, the pressure drop generated by the catalyst means 440 during operation can be kept small despite the small cross-sectional area of the passages become. The cross-sectional area of the inner cavity 451, which decreases linearly away from the inlet 437, results in an even distribution of the exhaust gas over the different passages and contributes to the fact that the exhaust gas is deflected largely without turbulence and with a small pressure loss and is distributed to the different passages 447. Because the inlet 437 and the inner cavity 451 have a common straight axis 432 and the exhaust gas flows essentially straight - ie without deflection - from the inlet into the inner cavity 451, there is only a small pressure loss between the inlet and the exhaust gas inlet surfaces of the catalyst means 440 formed by the four inner surfaces 441d. Furthermore, there is only a slight pressure loss between the outer surfaces 441c serving as exhaust gas exit surfaces of the catalyst means and the outlet 438. The catalyst therefore only causes a small pressure drop overall. Since the exhaust gas passes through the inlet without contacting the wall of the housing directly into the interior cavity 451 of the catalyst means 440 and since these are not in direct contact with the wall of the housing, the catalyst means 440 quickly become those for a catalytic on cold start Treatment of the exhaust gas heated temperature. It is also advantageous here that there is no limiting element corresponding to the boundary elements 250, 380, 420 in the inner cavity 451, which should also be heated during a cold start. The catalyst means 440 are also stable and robust and can be manufactured economically and installed in a housing at low cost. The fact that the catalyst means can be installed in the metallic housing without having to place a special heat and / or sound-insulating intermediate layer between the wall of the housing and the catalyst means also contributes to cost-effective manufacture.

The catalyst body 471 partially shown in FIGS. 20 and 21 can, for example, have a similar outline shape as the catalyst body 211 shown in FIGS. 1 to 4 and thus form a prism, the base of which consists of an oblique-angled parallelogram. The catalyst body 471 has a package of alternately successive, first sheet metal elements 473 and second sheet metal elements 474, which have the same outline shape as that Base area of the prism. Each first sheet metal element 473 has a main section 473a with elevations which consist of projections 473b which are distributed uniformly over the main section 473a, at least most of which are at a distance from the edges of the sheet metal element 473 and are delimited by self-contained, for example circular, contour lines. In the section shown in FIG. 21, humps 473b projecting alternately upwards and downwards follow one another. Each first sheet metal element 473 thus has bosses 473b projecting in opposite directions from a central plane of the first sheet metal element and from the regions of the first sheet metal element located between adjacent bumps. Each first sheet metal element 473e also has, for example, two flat holding sections 473 arranged at its shorter edges. The second sheet metal elements 474 are essentially flat. The sheet metal elements 473, 474 are held together by holding means which, for example, have spacer elements 475 which are arranged between the holding sections 473e and the holding sections of the second sheet metal elements 474 which are opposite them and are welded to the sheet metal elements. The catalyst body 471 has a group of passages 477 which run from one to the other longitudinal edges of the sheet metal elements.

It is possible to arrange two catalyst bodies 471 designed according to FIGS. 20, 21 analogously to the catalyst bodies 211 in a housing of a catalyst such that they together form V-shaped catalyst means. However, it is also possible for all other catalyst bodies shown in FIGS. 5 to 18 to provide the first sheet-metal elements with bosses corresponding to the bosses 473b instead of waves.

The catalysts can be modified in other ways.

For example, the first could be parallel to the axis Side and / or longitudinal walls 204a, 264a of the housing 203 and 263 are replaced by side or longitudinal walls which approach each other and the axis away from the inlet.

Furthermore, features of various catalysts shown in the figures can be combined with one another in a variety of ways. For example, the flat, first side and / or longitudinal walls 204a in FIGS. 1 to 3 can replace catalytic converter 201 with side and / or longitudinal walls bent in cross section, such as those shown in FIGS. 7 to 12 Catalysts are present.

Furthermore, the passages of the catalysts shown in FIGS. 1 to 6, 11, 12, 13, 14 can be replaced by passages which form an angle with planes perpendicular to the axis, which is preferably at most 45 ° and for example at most 30 °.

The outer and inner surfaces of the catalyst bodies of the catalysts shown in FIGS. 13 and 14 could be flat instead of curved in cross section. The internal cavities 381 and 421 are then essentially polygonal in cross-section, i.e. triangular or square, instead of circular. The mouth openings of the inlets opening into the inner cavities should then be triangular or quadrangular in cross-section instead of circular and have the same cross-sectional dimensions as the inner cavities. The paraboloidal boundary elements 380 or 420 of these catalysts could then possibly be replaced by an approximately triangular or square-shaped firing body, so that the cross-sectional area of the free area of the inner cavity again decreases at least approximately linearly and preferably exactly linearly with the distance from the inlet.

With the catalytic converter according to FIG. 13 one could do that Omit limiting element 380 and provide the three catalytic converter bodies with external and internal surfaces for this purpose, which approach the axis and towards one another away from the inlet analogously to the catalytic converters according to FIGS. 7 to 9 and 15 to 19.

In the case of the catalyst shown in FIG. 15, one could possibly replace the inlet 437, which consists of a cylindrical piece of pipe, with a nozzle which at least partially widens conically towards the catalyst means. Furthermore, one could possibly change the outlet 438 shown in FIG. 15 such that its end facing the catalyst means analogously to the outlets visible in FIGS. 1, 2, 5, 7, 11 only extends to the second end wall 436 and therefore not protrudes into the interior of the housing 433. The catalyst means 440 would then only be attached to the inlet 437 and not to the outlet. If necessary, the end of the catalytic means 440 facing the outlet could be connected to the jacket 434 and / or the second end wall 436 by some connecting elements, which consist of bolts or the like and are distributed around the axis 432.

In the case of the catalysts and / or catalyst means shown in FIGS. 1 to 14, one could provide the inlet and possibly the outlet with a piece of pipe or socket protruding into the interior of the housing, as is shown for the catalyst 431 in FIG. 15 and attach the catalyst means to these pipe pieces or connecting pieces in such a way that they are at a distance from both end walls and, for example, from the casing of the housing.

Furthermore, possibly more than four catalyst bodies, each with a group of passages, can be provided and distributed around an axis analogously to the catalysts according to FIGS. 7 to 19, so that they together enclose an internal cavity.

The welded connections which connect the sheet metal and spacer elements of the catalyst bodies to one another can be replaced by brazed connections or, in certain variants, by clamp connections. The holding means can then also have bolts for producing clamping connections which penetrate the sheet metal and spacer elements. It may even be possible to provide holding means - for example bolts and spacer rings - which cross and / or divide some exhaust gas passages of the catalyst means. These passages crossed by elements of the holding means can then possibly be a little shorter than the other passages.

In the case of the catalyst means described with reference to FIGS. 1 to 19, the nesting planes defined by the sheet metal elements and nestling on their surfaces and also the flat sheet metal elements themselves are parallel to the axis of the catalysts and catalyst means. However, one could arrange the sheet metal elements at least in the case of the catalyst bodies having flat inner and outer surfaces in such a way that the nesting planes defined by the sheet metal elements and conforming to them and the flat sheet metal elements themselves form an angle with the axis of the catalysts and catalyst means and for example 1 to 3 in the form of a V-shaped catalyst body at right angles to the walls 204b of the housing and either at right angles to the axis 202 or at right angles to the inner surfaces 211d and outer surfaces 211c. The waves can then run parallel to the walls 204b from the inner cavity 221 to the outer cavity 222, as in the case of the catalyst bodies shown.

Claims (18)

Catalytic converter for the catalytic treatment of exhaust gas, with a housing (203, 233, 263, 293, 303, 363, 403, 433) and catalyst means arranged in this (210, 240, 270, 295, 310, 370, 410, 440) , wherein an inner cavity (221, 251, 281, 321, 381, 421, 451) located at least partially between areas of the catalyst means (210, 240, 270, 295, 310, 370, 410, 440) and one between the catalyst means (210, 240, 270, 295, 310, 370, 410, 440) and at least a part of the housing (203, 233, 263, 293, 303, 363, 403, 433), external cavity (222 , 252, 282, 322, 382, 422, 452) are present, the catalyst means (210, 240, 270, 295, 310, 370, 410, 440) having sheet metal elements (213, 214, 443, 473, 474), the passages leading from the inner cavity (221, 251, 281, 321, 381, 421, 451) to the outer cavity (222, 252, 282, 322, 382, 422, 452) (217, 247, 277, 317, 377, 417, 447, 477), and at least one sheet metal element (213, 443 , 473) of each pair of adjacent sheet metal elements (213, 214, 443, 473, 474) has elevations, characterized in that the catalyst means (210, 240, 270, 295, 310, 370, 410, 440) at least two packages of Sheet metal elements (213, 214, 443, 473, 474) have that the sheet metal elements (213, 214, 443, 473, 474) belonging to the same package are defined by the clinging planes that are parallel to each other and that the passageways delimited by the different packages (217, 247, 277, 317, 377, 417, 447, 477) run on different sides of the inner cavity (221, 251, 281, 321, 381, 421, 451) away from it. Catalyst according to claim 1, characterized in that the different packages of sheet metal elements (213, 214, 443, 473, 474) at least in the in the outer cavity (222, 252, 282, 322, 382, 422, 452) opening ends of the passages (217, 247, 277, 317, 347, 377, 417, 447, 477) are at a distance from one another which is substantially larger than that Distance from adjacent sheet metal elements (213, 214, 443, 473, 474) belonging to one and the same package. Catalyst according to claim 1 or 2, characterized in that the sheet metal elements (213, 214, 443, 473, 474) belonging to the same package and adjacent to one another come into contact at nestling levels. Catalytic converter according to one of claims 1 to 3, characterized in that each packet has alternating successive, first, raised plate elements (213, 443, 473) and second, flat plate elements (214, 474). Catalyst according to one of claims 1 to 4, characterized in that the elevations are formed by waves (213b) and that the waves (213b) belonging to one and the same sheet metal element (213, 443) are parallel to one another. Catalyst according to one of claims 1 to 5, characterized in that each sheet metal element (213, 214, 443, 473, 474) in a projection which clings to the sheet metal element (213, 214, 443, 473, 474) concerned Is at right angles, has two straight, parallel edges. Catalyst according to claim 6, characterized in that each sheet metal element (213, 214, 443, 473, 474) is square in shape in the above-mentioned projection and has two other, straight, mutually parallel edges. Catalyst according to one of claims 1 to 7, characterized in that the different packets on the inner Cavity (281, 321, 381, 421, 451) have adjacent inner surfaces (271d, 311d, 371d, 411d, 441d), which together in cross-section essentially completely and without gaps, the inner cavity (281, 321, 381, 421, 451) enclose. Catalyst according to one of claims 1 to 8, characterized in that each packet of sheet metal elements (213, 214) has a flat inner surface (211d, 241d) adjacent to the inner cavity (221, 251) and a plane parallel to this, on the Has outer cavity (222, 252) adjacent outer surface (211c, 241c) and that the passages (217, 247) in the inner surface (211d, 241d) and in the outer surface (211c, 241c) have openings. Catalyst according to one of claims 1 to 9, characterized in that the catalyst means (370, 410, 440) have at least three packages of sheet metal elements (443) adjoining the inner cavity (381, 421, 451). Catalyst according to one of claims 1 to 10, characterized in that an inlet (207, 237, 267, 307, 437) with an interior and opening into the inner cavity (221, 251, 281, 321, 381, 421, 451) there is an outlet (208, 238, 268, 308, 438) with an interior connected to the outer cavity (222, 252, 282, 322, 382, 422, 452) such that the inner cavity (221, 251, 281, 321, 351, 381, 421, 451) has at least one free area adjoining the catalyst means (210, 240, 270, 295, 310, 340, 370, 410, 440), the cross-sectional area of which is from the inlet (207, 237, 267 , 307, 437) decreases, and that the interior of the inlet (207, 237, 267, 307, 437) at its mouth opening into the inner cavity (221, 251, 281, 321, 351, 381, 421, 451) has substantially the same cross-sectional shape and substantially the same cross-sectional dimensions as the inner cavity (221, 251, 281, 321, 351, 381, 421, 451). The catalyst of claim 11, characterized in that the cross-sectional area of the or each free region of the inner cavity (221, 251, 281, 321, 351, 421, 451) extends substantially along its entire length from the inlet (207, 237, 267, 307 , 437) diminishing dimension substantially linearly with the distance from the inlet (207, 237, 267, 307, 437). Catalyst according to claim 11 or 12, characterized in that the interior of the inlet (207) and the inner cavity (221) form a polygon in cross section at the opening of the interior of the inlet (207) opening into the latter. Catalyst according to claim 11 or 12, insofar as these are dependent on one of claims 1 to 8 or 10, characterized in that the interior of the inlet (267, 307, 437) and the inner cavity (281, 321, 381, 421, 451 ) are circular in cross section at the mouth of the inlet (267, 307, 437) opening into the latter. Catalyst according to one of claims 11 to 14, characterized in that the various packets adjacent to the inner cavity (221, 281, 451) in the direction away from the inlet (207, 267, 437) approaching inner surfaces (211d, 271d, 441d) ) to have. Catalyst according to one of claims 11 to 14, characterized in that the catalyst means (240, 310, 370, 410) define an axis (232, 302, 362, 402) that the packets parallel to this, to the inner cavity (251 , 321, 381, 421) adjacent inner surfaces (241d, 311d, 371d, 411d) have that in the inner cavity (251, 321, 381, 421) a limiting element (250, 320, 380, 420) is arranged and together with the inner surfaces (241d, 311d, 371d, 411d) facing it delimit at least one free area of the inner cavity (251, 321, 381, 421) and that the Bounding element (250, 320, 380, 420) approaches from the inlet (237, 307) to the inner surface (241d, 311d, 371d, 411d). Catalyst according to one of claims 1 to 16, characterized in that the housing (433) has a wall, that an inlet (437) with a rigidly and tightly connected to the wall of the housing (433) is present, which is in one of the Housing (433) enclosed interior protrudes that the catalyst means (440) are attached to the nozzle and are spaced on all sides from the wall of the housing (433) and that the inlet (437) opens into the inner cavity (451). Catalyst according to one of claims 1 to 17, characterized in that the sheet metal elements (213, 214, 443, 473, 474) have coatings with catalytically active material and that each sheet metal element (213, 214, 443, 473, 474) has at least one flat Holding section (213e, 213f, 214e, 214f, 473e), which on a flat holding section (213e, 213f, 214e, 214f, 473e) of another sheet metal element (213, 214, 443, 473, 474) and / or on an element (215, 475) of holding means, and that the abutting holding sections (213e, 213f, 214e, 214f, 473e) and elements (215, 475) are rigidly connected to one another.

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